Experimental verification of the Acuros XB and AAA dose calculation adjacent to heterogeneous media for IMRT and RapidArc of nasopharygeal carcinoma
Experimental verification of the Acuros XB and AAA dose calculation adjacent to heterogeneous media for IMRT and RapidArc of nasopharygeal carcinoma
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DOI：
10.1118/1.4792308
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发表时间：
2013-03-01
期刊：
影响因子：
3.8
通讯作者：
Yu, Peter K. N.
中科院分区：
文献类型：
--
作者：
Kan, Monica W. K.;Leung, Lucullus H. T.;Yu, Peter K. N.
目的：比较Acuros XB（AXB）算法和分析各向异性算法（AAA）计算的剂量与使用调强放射治疗（IMRT）和RapidArc（R）（RA）体积弧治疗计划治疗鼻咽癌（NPC）时邻近和异质介质内的实验测量数据。用GafChromic（R）EBT 3膜还使用热发光剂量计（Thermo-Luminescent Dosemeter，简称EBT）和EBT 3膜测量了含有异质介质的拟人模型的鼻泪管（NP）区域附近和内部的剂量。将测量数据与AAA和AXB计算的数据进行比较。对于AXB，使用剂量-培养基（AXB_D-m）和剂量-水（AXB_D-w）选项进行剂量计算。此外，针对相应的真实的患者，分析了AAA和AXB之间的靶剂量差异。通过将目标分层为不同密度的成分（包括组织、骨和空气）来执行真实的患者计划的比较。对于使用矩形体模验证空气和骨附近的平面剂量分布，通过伽马分析（+/- 3%/3 mm标准）的像素百分比分别为98.7%，99.5%，在所有IMRT和RA计划上，AAA、AXB_D-m和AXB_D-w在轴向平面上的平均显示率分别为97.6%、98.2%和97.7%，而在冠状平面上分别为97.6%、98.2%和97.7%。对于拟人化体模NP区域内平面剂量分布的验证，AAA、AXB_D-m和AXB_D-w通过伽马分析的像素百分比分别为95.1%、91.3%和99.0%，符合+/- 3%/3 mm标准，并在所有IMRT和RA计划上取平均值。在空气和骨存在的NP区域内，胶片测量代表接近非均匀介质中单位密度水的剂量，与AXB_D-W最一致。对于在拟人体模中使用放射性核素验证靶点内的点剂量，对于AAA、AXB_D-m和AXB_D-w，当对所有IMRT和RA计划取平均值时，计算数据和测量数据之间的绝对百分比偏差分别为1.8%、1.7%和1.8%。从所有的验证结果来看，调强放射治疗计划和RA计划之间没有显著差异。对真实的患者计划的靶剂量分析表明，在三种剂量计算选项中，组织中PTV组分的平均剂量差异在2%以内，但在骨含量中高达约4%，AXB_D-m给出最低值，AXB_D-w给出最高值。一般而言，验证测量结果表明，与测量数据相比，两种算法均产生了可接受的准确度。GafChromic（R）胶片结果表明，对于邻近非均匀介质和非均匀介质内的剂量计算，AXE的准确性略高于AAA。用户应了解选项AXB_D-m和AXB_D-w之间计算目标剂量的差异，尤其是在NPC病例中IMRT和RA的骨中。(C)2013年美国医学物理学家协会。[http//dx.doi.org/10.1118/1.4792308]
Purpose: To compare the doses calculated by the Acuros XB (AXB) algorithm and analytical anisotropic algorithm (AAA) with experimentally measured data adjacent to and within heterogeneous medium using intensity modulated radiation therapy (IMRT) and RapidArc (R) (RA) volumetric arc therapy plans for nasopharygeal carcinoma (NPC).Methods: Two-dimensional dose distribution immediately adjacent to both air and bone inserts of a rectangular tissue equivalent phantom irradiated using IMRT and RA plans for NPC cases were measured with GafChromic (R) EBT3 films Doses near and within the nasopharygeal (NP) region of an anthropomorphic phantom containing heterogeneous medium were also measured with thermo-luminescent dosimeters (TLD) and EBT3 films. The measured data were then compared with the data calculated by AAA and AXB. For AXB, dose calculations were performed using both dose-to-medium (AXB_D-m) and dose-to-water (AXB_D-w) options. Furthermore, target dose differences between AAA and AXB were analyzed for the corresponding real patients. The comparison of real patient plans was performed by stratifying the targets into components of different densities, including tissue, bone, and air.Results: For the verification of planar dose distribution adjacent to air and bone using the rectangular phantom, the percentages of pixels that passed the gamma analysis with the +/- 3%/3mm criteria were 98.7%, 99.5%, and 97.7% on the axial plane for AAA, AXB_D-m, and AXB_D-w, respectively, averaged over all IMRT and RA plans, while they were 97.6%, 98.2%, and 97.7%, respectively, on the coronal plane. For the verification of planar dose distribution within the NP region of the anthropomorphic phantom, the percentages of pixels that passed the gamma analysis with the +/- 3%/3mm criteria were 95.1%, 91.3%, and 99.0% for AAA, AXB_D-m, and AXB_D-w, respectively, averaged over all IMRT and RA plans. Within the NP region where air and bone were present, the film measurements represented the dose close to unit density water in a heterogeneous medium, produced the best agreement with the AXB_D-W. For the verification of point doses within the target using TLD in the anthropomorphic phantom, the absolute percentage deviations between the calculated and measured data when averaged over all IMRT and RA plans were 1.8%, 1.7%, and 1.8% for AAA, AXB_D-m and AXB_D-w, respectively. From all the verification results, no significant difference was found between the IMRT and RA plans. The target dose analysis of the real patient plans showed that the discrepancies in mean doses to the PTV component in tissue among the three dose calculation options were within 2%, but up to about 4% in the bone content, with AXB_D-m giving the lowest values and AXB_D-w giving the highest values.Conclusions: In general, the verification measurements demonstrated that both algorithms produced acceptable accuracy when compared to the measured data. GafChromic (R) film results indicated that AXE produced slightly better accuracy compared to AAA for dose calculation adjacent to and within the heterogeneous media. Users should be aware of the differences in calculated target doses between options AXB_D-m and AXB_D-w, especially in bone, for IMRT and RA in NPC cases. (C) 2013 American Association of Physicists in Medicine. [http//dx.doi.org/10.1118/1.4792308]